The present inventors have reported that (R)-2-(2-aminothiazol-4-yl)-4′-[2-[(2-hydroxy-2-phenylethyl)amino]ethyl]-acetanilide dihydrochloride represented by the following chemical structural formula has both an insulin secretion promoting action and an insulin sensitivity potentiating action, further has anti-obesity and anti-hyperlipemia actions due to a selective stimulating action to β3-receptors and is a useful compound for remedy of diabetes (WO 99/20607, Example 41).

However, since this dihydrochloride has strong hygroscopicity and is unstable, its use as a medicine was still problematic.
Medicines are required to be stable against humidity, temperature, light, and the like over a long period of time and also to have stability in the formulation step. If medicines have strong hygroscopicity, they physically and chemically change or cause such an inconvenience that the water content is different depending upon lots. Accordingly, it is necessary to always store them in a drying chamber or to provide a drying step, which is not preferable from the standpoint of industrial use.